Sometimes it's easier to do it all backwards: 

use strict;
use warnings;
use Data::Dumper;

my @a = ( 1, 2, 3, "a" );
my %Hash = do { my $hashref = 1;
                $hashref = { $_ => $hashref } for reverse @a;
                %{$hashref};
};

print Dumper \%Hash;

[download]

This algorithm is very similar to one used to create linked lists, demonstrated in Mastering Algorithms with Perl, published by O'Reilly & Associates.

The way this works is by assigning your final value to $hashref. Then you work backwards through @a, setting $hashref equal to $hashref->{a}=1, and then to $hashref->{3}{a}=1, and then to $hashref->{2}{3}{a}=1, and so on, each time adding one more higher layer. In the end, you asked for %Hash, not $hashref, so this snippet dereferences $hashref for you and hands you %Hash. The do{...} block is used to limit the scope of $hashref, and to compartmentalize the entire operation in one nice little package.

Enjoy!


Dave

In reply to Re: Hash key manipulation question by davido
in thread Hash key manipulation question by EchoAngel

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post, it's "PerlMonks-approved HTML":


  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.